/*
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License Version 2.0 with LLVM Exceptions
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *   https://llvm.org/LICENSE.txt
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#pragma once

#include <unifex/bind_back.hpp>
#include <unifex/finally.hpp>
#include <unifex/scheduler_concepts.hpp>
#include <unifex/tag_invoke.hpp>

#include <type_traits>

#include <unifex/detail/prologue.hpp>

namespace unifex {
namespace _via {
struct _fn {
  template(typename Source, typename Scheduler)         //
      (requires tag_invocable<_fn, Source, Scheduler>)  //
      auto
      operator()(Source&& source, Scheduler&& scheduler) const
      noexcept(is_nothrow_tag_invocable_v<_fn, Source, Scheduler>)
          -> tag_invoke_result_t<_fn, Source, Scheduler> {
    return tag_invoke(
        *this,
        static_cast<Source&&>(source),
        static_cast<Scheduler&&>(scheduler));
  }

  template(typename Source, typename Scheduler)           //
      (requires(!tag_invocable<_fn, Source, Scheduler>))  //
      auto
      operator()(Source&& source, Scheduler&& scheduler) const
      noexcept(noexcept(finally(
          static_cast<Source&&>(source),
          schedule(static_cast<Scheduler&&>(scheduler)))))
          -> decltype(finally(
              static_cast<Source&&>(source),
              schedule(static_cast<Scheduler&&>(scheduler)))) {
    return finally(
        static_cast<Source&&>(source),
        schedule(static_cast<Scheduler&&>(scheduler)));
  }
  template(typename Scheduler)         //
      (requires scheduler<Scheduler>)  //
      constexpr auto
      operator()(Scheduler&& scheduler) const
      noexcept(is_nothrow_callable_v<tag_t<bind_back>, _fn, Scheduler>)
          -> bind_back_result_t<_fn, Scheduler> {
    return bind_back(*this, (Scheduler &&) scheduler);
  }
};
}  // namespace _via

inline constexpr _via::_fn via{};
}  // namespace unifex

#include <unifex/detail/epilogue.hpp>
